Commit 0ceea87e authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Jialin Zhang
Browse files

objtool/x86: Fix SRSO mess 

stable inclusion
from stable-v5.10.193
commit c6aecc29d29eeda6b963f1a5ea0adae2e9fd7c3d
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I7RQ67

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c6aecc29d29eeda6b963f1a5ea0adae2e9fd7c3d



--------------------------------

commit 4ae68b26 upstream.

Objtool --rethunk does two things:

 - it collects all (tail) call's of __x86_return_thunk and places them
   into .return_sites. These are typically compiler generated, but
   RET also emits this same.

 - it fudges the validation of the __x86_return_thunk symbol; because
   this symbol is inside another instruction, it can't actually find
   the instruction pointed to by the symbol offset and gets upset.

Because these two things pertained to the same symbol, there was no
pressing need to separate these two separate things.

However, alas, along comes SRSO and more crazy things to deal with
appeared.

The SRSO patch itself added the following symbol names to identify as
rethunk:

  'srso_untrain_ret', 'srso_safe_ret' and '__ret'

Where '__ret' is the old retbleed return thunk, 'srso_safe_ret' is a
new similarly embedded return thunk, and 'srso_untrain_ret' is
completely unrelated to anything the above does (and was only included
because of that INT3 vs UD2 issue fixed previous).

Clear things up by adding a second category for the embedded instruction
thing.

Fixes: fb3bd914 ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230814121148.704502245@infradead.org


Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarJialin Zhang <zhangjialin11@huawei.com>
parent d3b2e775

tools/objtool/arch.h

+1 −0
Original line number Diff line number Diff line
@@ -90,6 +90,7 @@ int arch_decode_hint_reg(u8 sp_reg, int *base); 


bool arch_is_retpoline(struct symbol *sym);

bool arch_is_rethunk(struct symbol *sym);

bool arch_is_embedded_insn(struct symbol *sym);



int arch_rewrite_retpolines(struct objtool_file *file);

tools/objtool/arch/x86/decode.c

+7 −4
Original line number Diff line number Diff line
@@ -661,8 +661,11 @@ bool arch_is_retpoline(struct symbol *sym) 


bool arch_is_rethunk(struct symbol *sym)

{

	return !strcmp(sym->name, "__x86_return_thunk") ||

	       !strcmp(sym->name, "srso_untrain_ret") ||

	       !strcmp(sym->name, "srso_safe_ret") ||

	       !strcmp(sym->name, "retbleed_return_thunk");

	return !strcmp(sym->name, "__x86_return_thunk");

}



bool arch_is_embedded_insn(struct symbol *sym)

{

	return !strcmp(sym->name, "retbleed_return_thunk") ||

	       !strcmp(sym->name, "srso_safe_ret");

}

tools/objtool/check.c

+21 −1
Original line number Diff line number Diff line
@@ -945,16 +945,33 @@ static int add_ignore_alternatives(struct objtool_file *file) 
	return 0;

}



/*

 * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol

 * will be added to the .retpoline_sites section.

 */

__weak bool arch_is_retpoline(struct symbol *sym)

{

	return false;

}



/*

 * Symbols that replace INSN_RETURN, every (tail) call to such a symbol

 * will be added to the .return_sites section.

 */

__weak bool arch_is_rethunk(struct symbol *sym)

{

	return false;

}



/*

 * Symbols that are embedded inside other instructions, because sometimes crazy

 * code exists. These are mostly ignored for validation purposes.

 */

__weak bool arch_is_embedded_insn(struct symbol *sym)

{

	return false;

}



#define NEGATIVE_RELOC	((void *)-1L)



static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
@@ -1171,7 +1188,7 @@ static int add_jump_destinations(struct objtool_file *file) 
			 * middle of another instruction.  Objtool only

			 * knows about the outer instruction.

			 */

			if (sym && sym->return_thunk) {

			if (sym && sym->embedded_insn) {

				add_return_call(file, insn, false);

				continue;

			}
@@ -1970,6 +1987,9 @@ static int classify_symbols(struct objtool_file *file) 
			if (arch_is_rethunk(func))

				func->return_thunk = true;



			if (arch_is_embedded_insn(func))

				func->embedded_insn = true;



			if (!strcmp(func->name, "__fentry__"))

				func->fentry = true;

tools/objtool/elf.h

+1 −0
Original line number Diff line number Diff line
@@ -61,6 +61,7 @@ struct symbol { 
	u8 return_thunk      : 1;

	u8 fentry            : 1;

	u8 kcov              : 1;

	u8 embedded_insn     : 1;

};



struct reloc {